Since the finale of Season 6 with the future of Ponies and Changelings becoming brighter than ever, I decided to come up with a small theory, mainly about the changeling cocoons, if you remember at the end of Season 6, most of the characters (being Twilight and her friends, the royal sisters and the royal family) looked like that they missed out on what happened during the events of the finale, like they were asleep unconscious in the cocoons, but I have my own theory on how the cocoons work.

If one would remember the Season 2 finale (which debuted the Changeling race and their Queen), when the invasion was happening, Princess Celestia was incased in a changeling cocoon, and she was seeing what was happening outside before Chrysalis’s defeat.

The cocoon imprisonment was used again in the Season 6 finale, this time incasing the mentioned characters above, and while some may argue they were asleep or unconscious, if you remember looking closely, that Twilight and her friends and family were indeed awake, as their eyes were half opened.

For Discord's case, since he's a spirit of Chaos, he was wide awake, but just with a miserable look having been captured by the Changelings thanks to them using his weakness (being his friendship with Fluttershy).

I see how the imprisonment works, when prisoner(s) are incased in changeling cocoons far from a changeling habitat, the changeling magic on the cocoon is weak, allowing the prisoner(s) to see perfectly what’s going on outside (like what happened with Celestia during the invasion at Canterlot, but when imprisoned in a cocoon in an changeling habitat (the Changeling Kingdom for example), the changeling magic is stronger on the cocoon, and while the prisoner(s) still remains awake, it makes he/she/them a little drowsy (but not fully sleepy which can make them fall asleep), making their sight a little blurry and unable to see what’s happening, which explains what happened to Twilight and her friends and family when they were imprisoned in the changeling kingdom, since there was a stronger changeling magic there, while they were awake, they were a little drowsy and couldn’t figure out what was happening outside.

Hope those who are fans of the changelings as well as those like to learn about like this little info.

There are probably different kinds of cocoons. Capture ones that just hold someone, draining ones to drain love, healing ones that heal injured changelings, cocoons that turn other beings into changelings.